import org.checkerframework.checker.nullness.qual.*;

public class FlowLoop {
  void simpleWhileLoop() {
    String s = "m";

    while (s != null) {
      s.toString();
      s = null;
    }
    // :: error: (dereference.of.nullable)
    s.toString(); // error
  }

  void whileConditionError() {
    String s = "m";

    // :: error: (dereference.of.nullable)
    while (s.toString() == "m") { // error
      s.toString();
      s = null;
    }
    s.toString();
  }

  void simpleForLoop() {
    for (String s = "m"; s != null; s = null) {
      s.toString();
    }
  }

  void forLoopConditionError() {
    for (String s = "m";
        // :: error: (dereference.of.nullable)
        s.toString() != "m"; // error
        s = null) {
      s.toString();
    }
  }

  class Link {
    Object val;
    @Nullable Link next;

    public Link(Object val, @Nullable Link next) {
      this.val = val;
      this.next = next;
    }
  }

  // Both dereferences of l should succeed
  void test(@Nullable Link in) {
    for (@Nullable Link l = in; l != null; l = l.next) {
      Object o;
      o = l.val;
    }
  }

  void multipleRuns() {
    String s = "m";
    while (true) {
      // :: error: (dereference.of.nullable)
      s.toString(); // error
      s = null;
    }
  }

  void multipleRunsDo() {
    String s = "m";
    do {
      // :: error: (dereference.of.nullable)
      s.toString(); // error
      s = null;
    } while (true);
  }

  void alwaysRunForLoop() {
    String s = "m";
    for (s = null; s != null; s = "m") {
      s.toString(); // ok
    }
    // :: error: (dereference.of.nullable)
    s.toString(); // error
  }

  public void badIterator() {
    Class<?> opt_doc1 = null;
    // :: error: (dereference.of.nullable)
    opt_doc1.getInterfaces();
    Class<?> opt_doc2 = null;
    // :: error: (dereference.of.nullable)
    for (Class<? extends @Nullable Object> fd : opt_doc2.getInterfaces()) {
      // empty loop body
    }
  }

  void testContinue(@Nullable Object o) {
    for (; ; ) {
      // :: error: (dereference.of.nullable)
      o.toString();
      if (true) continue;
    }
  }

  void testBreak(@Nullable Object o) {
    while (true) {
      // :: error: (dereference.of.nullable)
      o.toString();
      if (true) break;
    }
  }

  void testSimpleNull() {
    String r1 = null;
    while (r1 != null) {}
    // :: error: (dereference.of.nullable)
    r1.toString(); // error
  }

  void testMulticheckNull() {
    String r1 = null;
    while (r1 != null && r1.equals("m")) {}
    // :: error: (dereference.of.nullable)
    r1.toString(); // error
  }

  void testAssignInLoopSimple() {
    String r1 = "";
    while (r1 != null) {
      r1 = null;
    }
    // :: error: (dereference.of.nullable)
    r1.toString(); // error
  }

  void testAssignInLoopMulti() {
    String r1 = "";
    while (r1 != null && r1.isEmpty()) {
      r1 = null;
    }
    // :: error: (dereference.of.nullable)
    r1.toString(); // error
  }

  void testBreakWithCheck() {
    String s = null;
    while (true) {
      if (s == null) break;
      s.toString();
    }
  }

  void test1() {
    while (true) {
      String s = null;
      if (s == null) {
        return;
      }
      s.toString();
    }
  }
}